The invention relates to a fluid flow machine.
The aerodynamic loads applied to fluid flow machines, such as for example fans, compressors, pumps and blowers that can be operated with a gaseous as well as with a liquid medium, is determined by the growth and separation of boundary layers on the blades as well as on the hub and housing walls. Usually, a good operational behavior can be obtained when the aerodynamic loading is evenly distributed to the rotor blading and the stator blading, for example in a fan stage or compressor stage. What mostly occurs here is a decrease of the flow path's cross-sectional area in flow direction, which is necessary with a compressible working medium between the entry and the exit plane of a stage, similar at the rotor and the stator.
The stability limit of fluid flow machines such as fans, compressors, pumps and blowers is significantly determined by the choice of the profile angle of the blading and the resulting loading and utilisation factor (performance). For this reason, threshold values that are based on the designing experience of successful machines are usually not exceeded. This applies in the same way and according to the state of the art also to a similar degree to the rotor blade rows as well as stator blade rows of a fluid flow machine. The correspondingly used threshold values for rotors and stators according to the state of the art entail a course of the main flow path (formed by the hub and housing contour of the machine) that extends in a smooth and continuous manner and barely shows any differences to the downstream flow cross-section changes in rotors and stators. Thus, at a given rotor blade speed, the possible stage pressure conditions are limited to values that have already been long known.
DE 10 2009 033 591 A1 describes a fluid flow machine with at least one blade row group in which the area cross section of the main flow path in at least one stage of the fluid flow machine leads to an excessive rotor-stator necking ratio.
There is a need to provide a fluid flow machine that implements a new manner of relating the blade angle and the course of the main flow path area to each other.